Pumps for vacuum veneering

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Wondering if I can do vacuum-press veneering on the cheap.... Has anybody tried using this
http://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connector s-96677.html
or something similar as the vacuum source? Any reasons why it wouldn't do the job? (Other than the fact that it comes from Horrible Fright, of course.)
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The comments were telling.... a big compressor is needed seems to be a theme and I thought this somewhat negative one was amusing...
"i bought this to replace compressor in a friends car so i wouldnt have to carry my $8000 snap o unit around. and wow...my girl friend can pull a deeper vacuum than this thing, even used a 60 gallon 2 stage compressor."
Perhaps this one...?
http://www.harborfreight.com/two-stage-3-cfm-air-vacuum-pump-66466.html
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I already have a decent-sized 240V compressor, so that may not be too much of an issue.

I did see that comment. :-) Most of the other purchasers seemed reasonably satisfied, though.

Saw that too. Didja see the difference in the price tags, though? ;-)
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Yes... but you don't need the big compressor which may or may not be an issue for you. My PC compressor would never keep up but my father's big Ingersoll Rand (that came out of a meat packing plant) would. I'd need 3 miles of hose though. ;~) That makes the self contained HF unit more attractive. I've been exploring options too and am taking cues from some of the wood turners I know. They have gotten rebuilt high-end vacuum pumps for use as vacuum chucks. Most of those guys are "cheap" but they are engineers so I think they probably over-researched things before settling on this solution. Some of them are vocal about being turners because they can get most of their wood for free. ;~)
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On Fri, 24 Feb 2012 09:08:39 -0500, "John Grossbohlin"

the job.
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On Fri, 24 Feb 2012 06:39:40 -0800 (PST), Robatoy

Is that your normal holddown method? Wow, 25 microns is a superb unit. We used to try to get at least 28 inches of mercury for auto air conditioning system pulldown after repairs. That's 49,000 microns. Most of the time, we'd get 29", but 28 was minimum, IIRC. It has been 30 years since I've done one.

Those seem like a complete waste of energy, air, and compressor life, not to mention that they're damned loud. I've only heard one once, a $10 HF job, and that was enough to dislike the whole concept.

Air tanks for the bags sound like a great idea for quick control of a sticky glueup.

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Oh, that's what that means.
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Doug Miller wrote:

When I saw an example of vacuum veneering in a book my first though was - this looks like those zip-lock vacuum bags. Why wouldn't they work? I mean tons of pressure is not needed - mostly even pressure. But those are just thoughts since I have never tried vacuum veneering.
Mike
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They *do* work for small projects (anything that will fit inside the bag...). I've done several projects this way. I never got around to cutting a valve out of a bag and using it for a bigger project. The only problem is that the valve section needs to be on a flat area for the valve to seal (it's a simple one-way flap valve). I've also used a Mityvac hand punp (http://www.mityvac.com /), but it will make you tired *quick*!

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On Fri, 24 Feb 2012 09:34:37 -0500, "parksfamily2 ------ ---- --- gmail ----- ----- com" <"parksfamily2 ------ ---- --- gmail ----- ----- com"> wrote:

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Doug Miller wrote:

water flow instead of air flow (venturi principle). And quieter.
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Interesting idea, but I think I'd prefer to keep water hoses out of the wood shop. :-)
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Two things you need to know.
1 will this require the refrigerant as a lube. 2 how noisy is this. I have a 2 stage medical pump that I use. It's so quite. 3 can it run full time. If not you can build a reservoir which will make it more intermittent.
Good luck, seems like the right amount of pull.
On 2/24/2012 8:07 AM, Doug Miller wrote:

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Sorry didn't see it was a venturi operated unit. That changes things.
On 2/24/2012 10:25 AM, tiredofspam wrote:

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Look in the yellow pages for someone who services or rebuilds small offset duplicator printing presses. These presses use vane pumps to create a vacuum to lift the paper into the press. Vane pumps last forever, a press can run two shifts a day for 10 years on the same pump with little service. These same pumps are also used for vacuum contact film duplication by printers and for vacuum plate making, which is really the same as veneering. The pump creates a vacuum between film and the printing plate and holds it until the plate is "burned", 5 to 10 minutes. Used ones can be cheap if you shop around. It will last forever if you keep the sawdust out of it.
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Vane pumps can move a lot of air quickly, but normally operate at medium vacuum. For veneering a couple of extra inches of mercury may be desirable.
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I don't know what you mean by "medium" vacuum. Most of the pumps used in small printing equipment will develop a vacuum of 20 inches of mercury, some more, how much do you need? The one I have is made by Gast.
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It does make some difference in the clamping force. A vacuum of 20 in Hg is only about 2/3 atmosphere, or about 10 psi pressure -- 28 in Hg is more like 0.94 atm, or about 13.8 psi.
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On Sat, 25 Feb 2012 04:20:29 +0000 (UTC), Doug Miller

veneer from curling. Too much vacuum forces all the glue out of the joint (or draws it through the pores in woods like red oak - making finishing difficult)
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snipped-for-privacy@snyder.on.ca wrote in

Your decimal point's in the wrong place. 10 psi = 1440 lb/sq ft.

I don't know enough about vacuum veneering to know whether that makes a difference or not, I was just pointing out that there is a substantial difference in pressure between 20 inches of vacuum, and 28.
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On Fri, 24 Feb 2012 22:35:38 -0500, "EXT"

for vacuum bagging fiber glass. A shop vac will produce 6 or 7 inches on a good day. What about combining the shop vac to pull the bag down quickly, then draw it down the rest of the way with a diaphragm pump or a Gast type pump - or even an old refrigerator unit. see: http://www.paragoncode.com/shop/vacuum_pump /
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